Non-Derivative Fair Value Measurements (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2021	Jun. 30, 2021		Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Gain on Securities	$ 981	$ 1,200
Unrealized Loss on Securities	$ 5	3
Nuclear decommissinoning fund [Abstract]
Equity investments in unconsolidated subsidiaries		189		$ 165
Miscellaneous investments		162		154
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Due in one year or less		2
Due in 1 to 5 years		153
Due in 5 to 10 years		210
Due after 10 years		292
Total		657
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Cost
Nuclear decommissinoning fund [Abstract]
Decommissioning Fund Investments		1,850	[1]	1,801	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Cost | Cash equivalents
Nuclear decommissinoning fund [Abstract]
Cash equivalents		30	[1]	40	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Cost | Commingled funds
Nuclear decommissinoning fund [Abstract]
Commingled funds		800	[1]	787	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Cost | Debt securities
Nuclear decommissinoning fund [Abstract]
Debt securities		612	[1]	528	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Cost | Equity securities
Nuclear decommissinoning fund [Abstract]
Equity securities		408	[1]	446	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value
Nuclear decommissinoning fund [Abstract]
Alternative investment		1,164	[1]	1,041	[2]
Decommissioning Fund Investments		3,038	[1]	2,777	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Cash equivalents
Nuclear decommissinoning fund [Abstract]
Cash equivalents		30	[1]	40	[2]
Alternative investment		0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Commingled funds
Nuclear decommissinoning fund [Abstract]
Commingled funds		1,164	[1]	1,041	[2]
Alternative investment		1,164	[1]	1,041	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Debt securities
Nuclear decommissinoning fund [Abstract]
Debt securities		657	[1]	585	[2]
Alternative investment		0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Equity securities
Nuclear decommissinoning fund [Abstract]
Equity securities		1,187	[1]	1,111	[2]
Alternative investment		0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 1
Nuclear decommissinoning fund [Abstract]
Decommissioning Fund Investments		1,215	[1]	1,149	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 1 | Cash equivalents
Nuclear decommissinoning fund [Abstract]
Cash equivalents		30	[1]	40	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 1 | Commingled funds
Nuclear decommissinoning fund [Abstract]
Commingled funds		0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 1 | Debt securities
Nuclear decommissinoning fund [Abstract]
Debt securities		0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 1 | Equity securities
Nuclear decommissinoning fund [Abstract]
Equity securities		1,185	[1]	1,109	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 2
Nuclear decommissinoning fund [Abstract]
Decommissioning Fund Investments		643	[1]	574	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 2 | Cash equivalents
Nuclear decommissinoning fund [Abstract]
Cash equivalents		0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 2 | Commingled funds
Nuclear decommissinoning fund [Abstract]
Commingled funds		0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 2 | Debt securities
Nuclear decommissinoning fund [Abstract]
Debt securities		641	[1]	572	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 2 | Equity securities
Nuclear decommissinoning fund [Abstract]
Equity securities		2	[1]	2	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 3
Nuclear decommissinoning fund [Abstract]
Decommissioning Fund Investments		16	[1]	13	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 3 | Cash equivalents
Nuclear decommissinoning fund [Abstract]
Cash equivalents		0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 3 | Commingled funds
Nuclear decommissinoning fund [Abstract]
Commingled funds		0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 3 | Debt securities
Nuclear decommissinoning fund [Abstract]
Debt securities		16	[1]	13	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 3 | Equity securities
Nuclear decommissinoning fund [Abstract]
Equity securities		$ 0	[1]	$ 0	[2]

[1] Reported in nuclear decommissioning fund and other investments on the consolidated balance sheets, which also includes $189 million of equity method investments and $162 million of rabbi trust assets and miscellaneous investments.

[2] Reported in nuclear decommissioning fund and other investments on the consolidated balance sheets, which also includes $165 million of equity method investments and $154 million of rabbi trust assets and other miscellaneous investments.